Effect of high current pulsed electron beam treatment on surface microstructure and wear and corrosion resistance of an AZ91HP magnesium alloy

This paper reports an analysis of the microstructure and property modifications on a commercial Mg alloy AZ91HP treated by using High Current Pulsed Electron Beam (HCPEB). It is shown that, a thin layer consisting of nanograined MgO formed on the top surface after HCPEB (electron energy ∼ 30 keV, pulse duration 1 μs, energy density ∼ 3 J/cm2) treatment, below which is a melted layer with depth of about 8–10 μm. The heat affected zone (HAZ) underneath the melted layer and stress wave affected zone contains many stress induced deformation marks. Meantime, a nearly complete dissolution of the intermetallic phase Mg17Al12 in the melted layer is observed, leading to the formation of a super-saturated solid solution on the surface. This is due to the solute trapping effect occurred during the fast solidification process. As a result, the wear and corrosion resistance of the alloy were significantly improved as shown by sliding friction, wear and immersion tests.